JP2006017925A - Optical waveguide and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide which is applicable to downsizing and high integration of an optical communication element and an optical integrated circuit, and is further excellent in productivity, and to provide a manufacturing method to obtain the optical waveguide. <P>SOLUTION: Optical waveguide cladding section 15 to which a metal ion is implanted is formed on a quartz thin film 13 integrally formed with an optical waveguide core section 14. Furthermore, if necessary, on the route of these optical waveguides, an optical switch section constructed with a second buffer layer 16 formed on a part of the core section of the optical waveguide and a metal electrode film 17 with which an electric field is applicable to an upper section of the second buffer layer is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide using a quartz crystal thin film integrated by a vapor deposition method in a core portion or a cladding portion around the core portion, and a method for manufacturing the same. About.

  An optical communication device used for optical communication using an optical fiber, or an optical integrated circuit that realizes various functions by integrating optical devices such as optical switches and optical coupling and branching, between optical fibers or between optical fibers and electronic equipment. Many optical waveguides are used as a path connecting optical devices used in connected portions and optical integrated circuits.

  As a conventional optical waveguide, an optical waveguide having a groove structure formed by patterning an optical waveguide portion on a substrate (see Patent Document 1 below), and the optical waveguide portion around the optical waveguide portion is optically refracted. An optical waveguide having a clad structure covered with materials having different rates (see Patent Document 2 below) is used.

  As a method for manufacturing such an optical waveguide, a core layer is formed on a quartz glass wafer-shaped substrate. Next, the other core layer is removed from the substrate by photolithography and etching so that the core layer of the core layer remains on the substrate. Next, a method is used in which a clad layer is formed on the substrate and a core portion, and the optical waveguide is manufactured by casing the substrate thus formed with the optical waveguide.

  The following documents are disclosed about the above optical waveguide and its manufacturing method.

JP-A-6-167626 JP 2002-162526 A JP 2002-196168 A

  In addition, the applicant has not found any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the above prior art document information.

  However, in the conventional optical waveguide and the manufacturing method thereof described above, there is a limit to reducing the size of the cross section of the core portion of the optical waveguide, and there is a possibility that light is scattered in the core. When light is scattered, data loss and other devices near the optical waveguide may be adversely affected.

  Also, when miniaturizing and highly integrating the optical waveguide with a groove structure, it is difficult to maintain the processing finish accuracy of the side surface of the core at the light wavelength level. Even if processing is possible, the processing equipment is very It becomes expensive to realize a high processing level, and it becomes one of the factors that raise the product unit price

  Further, in the case of an optical waveguide having a clad structure in which a clad layer is formed around the core portion, a space for forming the clad layer is inevitably required around the core portion, which makes it very difficult to reduce the size, particularly to achieve high integration.

  Furthermore, in optical communication devices and optical integrated circuits, the optical switch part used for them is formed as a separate component from the optical waveguide part. Therefore, the process of forming the optical switch part is separate from the process of forming the optical waveguide. Necessary. Therefore, the manufacturing time and manufacturing cost for that amount are required, which may be a factor for increasing the unit price of the product.

  The present invention has been devised in view of the above-described drawbacks, and an object thereof is an optical waveguide that can cope with downsizing and high integration of an optical communication element and an optical integrated circuit, and has excellent productivity, and the optical waveguide. It is in providing the manufacturing method which can obtain.

As means for solving the above problems, an optical waveguide core portion formed on a substrate, an optical waveguide core portion covering at least a part of the optical waveguide core portion, and an optical waveguide cladding portion having a different optical refractive index are formed. In the optical waveguide
The optical waveguide core portion and the optical waveguide clad portion are formed of an integrally formed crystal thin film, and metal ions are implanted into the crystal thin film constituting the optical waveguide clad portion, and the optical waveguide core portion A desired position on the path is constituted by a second buffer layer formed above the optical waveguide core portion and a metal electrode film capable of applying an electric field to the upper portion of the second buffer layer. An optical waveguide characterized in that an optical switch portion is formed.

In addition, as a method of manufacturing the optical waveguide described in the preceding paragraph, an optical waveguide for forming a core portion formed of quartz on a substrate and a cladding portion that covers at least a part of the core portion and a clad portion having a different optical refractive index. In the manufacturing method,
A first buffer layer is formed on a mother substrate on which a plurality of element sub-substrates each having an optical waveguide formation region are provided in a matrix, and the first buffer layer is optically applied to each sub-substrate by photolithography. A step of exposing and developing a wiring pattern of a desired optical waveguide portion and optical switch portion in a waveguide formation region, and removing unnecessary portions other than the wiring pattern of the first buffer layer by etching;
A step of epitaxially forming a crystal thin film by vapor deposition on the mother substrate and the first buffer layer remaining on the mother substrate;
Forming a second buffer layer on the quartz thin film and forming an electrode film on the second buffer layer formed at a position where the optical switch portion is formed;
A step of forming an injection protective film on the crystal thin film and the electrode film used as the optical waveguide core portion for each optical waveguide forming region in each of the quartz thin films,
A step of injecting metal ions into the crystal thin film from above the crystal thin film and electrode film on which the implantation protective film is formed at a desired location on the surface, the implantation protective film is removed, and the mother substrate is formed into a desired region including the optical waveguide element forming region. It is also a manufacturing method characterized by comprising a step of simultaneously forming an element in which a plurality of optical waveguides are formed by cutting into a child substrate shape and casing the child substrate.

  According to the present invention, a crystal thin film formed by vapor deposition can be used for the core portion and the clad portion. Therefore, the size of the cross-sectional area of the core portion of the optical waveguide is much higher than that of the conventional one. It can be made small, light scattering in the core can be suppressed, and data loss due to the light scattering and adverse effects on other devices near the optical waveguide can be minimized.

  In addition, since the core and clad are formed on the quartz thin film integrally formed with the core and the clad by photolithography and patterning, the core and clad can be formed very finely and with high precision. In addition, it is possible to reduce the size of the optical integrated circuit and particularly to increase the integration.

  Furthermore, in the present invention, the optical switch part can be obtained by forming an electrode film on the optical waveguide at a desired location of the optical waveguide made of quartz, so that the optical switch part itself is manufactured as compared with the prior art. The process and the manufacturing cost can be remarkably shortened and lowered, and the structure of the optical switch part can be simplified, which is advantageous for downsizing and high integration.

  Therefore, the above action produces an effect of providing an optical waveguide that is superior in miniaturization and integration, and has a good manufacturing efficiency, and a method for manufacturing the same, as compared with a conventional optical waveguide.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of an optical waveguide manufactured by the manufacturing method of the present invention cut at right angles to the light traveling direction. FIG. 2 is a process chart showing the manufacturing process of the optical waveguide shown in FIG. In FIG. 1, for clarity of explanation, a part of the structure is not shown, and some dimensions are exaggerated. In particular, layers such as quartz thin films and film thickness dimensions are shown in a deformed form to facilitate understanding of the present invention.

  That is, in the optical waveguide shown in FIG. 1, the first buffer layer 12 is formed on the surface of the substrate 11 made of silicon, glass, alumina, or the like. The first buffer layer is processed into the desired wiring shape of the optical waveguide portion and the optical switch portion by photolithography and etching. The first buffer layer 12 is formed for improving the crystallinity of the crystal thin film 13 formed thereon.

  A quartz thin film 13 having a thickness of several μm is formed on the first buffer layer 12 by epitaxial growth by a vapor phase growth method. In this quartz crystal thin film 13, metal ions are formed on the optical waveguide core portion 14 in the quartz thin film formed on the first buffer layer and in the quartz crystal thin film formed on the substrate 1 other than on the first buffer layer. It is injected and processed into an optical waveguide cladding portion 15 having a different optical refractive index from that of the optical waveguide core portion 14.

  A second buffer layer 16 is formed on the crystal thin film 13 composed of the optical waveguide core portion 14 and the optical waveguide cladding portion. Further, an electrode film 17 made of gold is formed on the second buffer layer at a desired position of the optical waveguide core portion 14. By applying an electric field to the electrode film 17, distortion occurs in the crystal of the optical waveguide core portion 14 below the electrode film 17 due to the inverse piezoelectric effect, and the optical refractive index of the optical waveguide core portion 14 changes due to this distortion. To do. Therefore, an optical switch portion using this action is formed in the portion of the optical waveguide core where the electrode film 17 is formed.

  Next, a method for manufacturing the optical waveguide will be described with reference to FIG. First, a first buffer layer is formed on an entire surface of a mother substrate on which a sub-substrate of an optical communication device or an optical integrated circuit having a plurality of optical waveguide formation regions is provided in a matrix, and this first buffer layer is formed on a photo The pattern of the desired optical waveguide portion and the optical switch portion in the optical waveguide formation region of each sub-substrate is exposed and developed by lithography, and unnecessary portions other than the desired optical waveguide pattern of the first buffer layer are removed by etching ( Step (a) to step (c) in FIG. 2).

  Next, a quartz crystal thin film is desired on the mother substrate and the first buffer layer formed in a desired optical waveguide pattern remaining on the mother substrate by vapor phase growth using an apparatus as shown in FIG. Is epitaxially grown to a thickness (step (d) in FIG. 2). At this time, due to the influence of the first buffer layer, the crystallinity of the crystal thin film on the first buffer layer is better than the crystallinity of other portions, and the loss of light passing therethrough can be reduced.

  Next, a second buffer layer is formed on the quartz thin film, and an electrode film is formed on the second buffer layer at a predetermined position on the path of the optical waveguide core portion to be formed in a later step (FIG. 2). Step (e) to Step (f)). The optical switch part in the present invention is formed by utilizing the change of the optical refractive index by utilizing the inverse piezoelectric effect by the crystal thin film forming the electrode film and the optical waveguide core part.

  Next, among the crystal thin films formed on the entire mother substrate, the second buffer layer used as the optical waveguide core portion and the electrode film formed as the optical switch portion for each optical waveguide formation region in each sub-substrate are injected. A protective film is formed (step (g) in FIG. 2).

  Next, metal ions are implanted as impurities into the crystal thin film from above the second buffer layer having the implantation protective film formed at a predetermined position on the surface and the electrode film (step (h) in FIG. 2). Metal ions are injected into the crystal thin film other than the portion protected by the implantation protective film, so that the presence or absence of metal ions is present between the protected crystal thin film portion and the unprotected quartz thin film portion into which the metal ions are implanted. This causes a difference in the refractive index of light. Using this difference, an optical waveguide core (without metal ions) and an optical waveguide cladding (with metal ions) are formed in the quartz thin film. By using such a forming method, the optical waveguide core portion and the optical waveguide clad portion can be formed finely and with high accuracy in the crystal thin film.

  Next, the injection protective film is removed from the second buffer layer and the electrode film (step (i) in FIG. 2), and the desired light including the optical waveguide forming region in which the optical waveguide is formed by the process as described above. Each sub-board of the communication device or the optical integrated circuit is cut, and an optical element in which a plurality of optical waveguides are formed by casing each cut sub-board is formed simultaneously (step (j) in FIG. 2).

  In this embodiment, as a method of forming the optical waveguide cladding portion, a method of injecting metal ions into the portion of the crystal thin film where the optical waveguide cladding portion is formed is disclosed. However, the present invention is not limited to this method. Alternatively, a substance other than the metal ion of the present embodiment may be used as long as it can be injected into the crystal thin film and the optical refractive index varies depending on the presence or absence of injection.

FIG. 1 is a cross-sectional view of an optical waveguide manufactured by the manufacturing method of the present invention cut at right angles to the traveling direction of an optical signal. 2 is a process chart showing a process of manufacturing the optical waveguide shown in FIG. FIG. 3 is a schematic diagram of an apparatus for performing epitaxial growth of a crystal thin film on a substrate mounted therein, in the method of manufacturing an optical waveguide according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Board | substrate 12 ... 1st buffer layer 13 ... Quartz thin film 14 ... Optical waveguide core part 15 ... Optical waveguide clad part 15 ... Mother board 16 ... 2nd buffer Layer 17 ... Electrode film

Claims (2)

In the optical waveguide in which the optical waveguide core part formed on the substrate, the optical waveguide core part covering at least a part of the optical waveguide core part, and the optical waveguide clad part having a different optical refractive index are formed.
The optical waveguide core portion and the optical waveguide clad portion are formed of an integrally formed crystal thin film, and metal ions are implanted into the crystal thin film constituting the optical waveguide clad portion, and the optical waveguide At a desired position on the path of the core portion, a second buffer layer formed on the optical waveguide core portion, and a metal electrode film capable of applying an electric field on the second buffer layer, An optical waveguide characterized in that an optical switch part constituted by the above is formed. In an optical waveguide manufacturing method for forming an optical waveguide core part formed of quartz on a substrate, and an optical waveguide clad part having a different optical refractive index from the optical waveguide core part covering at least a part of the optical waveguide core part,
A first buffer layer is formed on a mother substrate on which a plurality of element sub-substrates having optical waveguide formation regions are provided in a matrix, and the first buffer layer is formed on each sub-substrate by photolithography. Exposing and developing a wiring pattern of a desired optical waveguide in the optical waveguide formation region, and removing unnecessary portions other than the wiring pattern of the first buffer layer by etching; and
A step of epitaxially forming a crystal thin film on the mother substrate and the first buffer layer remaining on the mother substrate by vapor deposition;
Forming a second buffer layer on the quartz thin film and forming an electrode film on the second buffer layer formed at a position where the optical switch portion is formed at a desired position of the optical waveguide core portion; When,
A step of forming an injection protective film on the crystal thin film and the electrode film used as the optical waveguide core portion for each optical waveguide forming region in each of the sub-substrates of the crystal thin film;
Injecting metal ions into the crystal thin film from above the crystal thin film and the electrode film having the injection protective film formed at a desired location on the surface, removing the injection protective film, and forming the mother substrate into the optical waveguide element A method of manufacturing an optical waveguide, comprising: forming a plurality of optical waveguides at the same time by cutting into a desired sub-substrate shape including a formation region and casing the sub-substrate. .

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